1. Field of the Invention
The present invention relates to reed switch arrays, and more specifically, to a micro electromechanical systems (MEM's) reed switch array.
2. Prior Art
Reed switches are magnetically actuated switches, which are typically manufactured with two ferromagnetic reeds (contact blades) spaced a distance apart, which are sealed in a glass capsule. In the presence of a magnet, the blades (contacts) are deflected until they contact. This arrangement can be compromised by introducing a magnetic field with the same pole orientation as the magnet used in the assembly.
Reed switch types consist of dry reed or mercury wetted reed switches. A dry reed switch contains ferromagnetic contact blades sealed in a glass container with an inert gas. In a mercury wetted reed switch, mercury is the contact material for an electrical circuit. The contacting faces are renewed by capillary action drawing a film of mercury over the surfaces of the constant switching members as the movable contact member is moved from one position to another. The center position on reed switches can be center gap or off center gap. The gap is the contact meeting point of the switch.
Most current reed switch assemblies use a single form A reed switch that is a normally open (NO) switch. Some more expensive reed switch assemblies use a single form C reed switch that consists of a normally open (NO), normally closed (NC) and common connection. A normally open (NO) switch has contacts that are open or disconnected in their unactuated (normal) position. A normally closed (NC) switch has contacts that are closed or connected in their unactuated (normal) position. High security switches utilize arrays of form A and C reed switches and are much larger and significantly more expensive.
Conventional reed switches have a range of operation. These reed switches are mass produced and sorted by sensitivity (i.e. ampere turn) into various ranges. The tighter the sensitivity range, the more expensive the reed switch is. The preferred, i.e. more sensitive, switches also tend to be more expensive. As conventional reed switch arrays decrease in size, the cost increases and the range of sensitivity increases, and there is a greater variation in performance. In the manufacturing process, the glass also tends to fracture causing yield issues. To address the issue of tamper protection, high security contacts have been designed using arrays of reed switches which detect the introduction of another magnetic field. However, the cost of these switches is significant.
Thus, there remains a distinct need in the market for a reed switch array that has a small size, an increased range of sensitivity, tamper protection, and is less expensive to manufacture than existing solutions.